Manufacturers of devices such as mobile communication devices may perform test procedures at various points stages during device assembly. The manufacturing process may produce sub-assemblies of various components including integrated circuit (IC) devices and System-on-Chip (SoC) devices that may include processing circuits, user interface components, storage and other peripheral components that are tested before final assembly to obtain a finished device and/or before packaging for shipment. In some instances, a device may include one or more standardized interfaces that enable the device to communicate with peripherals or other devices in normal operations, and such standardized interfaces may be used by test equipment to control and monitor testing of the device. For example, test equipment may communicate with a processing device using a standardized serial port to input control information and commands, and to receive responses indicating progress of testing and indications of success or failure of a device or subassembly under test.
As the capabilities and complexity of mobile communication devices increase, the need for improved test capabilities has increased in proportion. However, the ability to use standardized interfaces for test purposes has been inhibited due to more stringent signaling and electrical specifications necessitated, for example, by a requirement that the communications interfaces be multifunctional and usable for attaching a broader range of peripherals through more complex communications protocols. In many instances, a device or subassembly may be required to be powered-on and operational before its communication interfaces can be used to facilitate or assist in the performance of test procedures.